Technical Abstract:
Recent reports show that biotin-dependent acetyl-coA carboxylase activity, the first step in fatty acid biosynthesis, is present both in apicoplasts (ACC1), and the cytosol (ACC2) in apicomplexan parasites such as Toxoplasma gondii and Plasmodium falciparum. A biotin-dependent pyruvate carboxylase is also located in mitochondria. Similar information on Eimeria sp is not available. We found that sporozoites and merozoites of avian Eimeria showed the presence of numerous discrete fluorescent areas when the parasites were stained with streptavidin-FITC, indicating the presence of biotin containing proteins. Lack of complete co-localization with the mitochondrial-targeting dye suggests these are proteins other than pyruvate carboxylase. Equal protein aliquots of oocyst, sporozoite and merozoite soluble extracts were separated by SDS-PAGE. Staining with avidin-peroxidase revealed the presence of three bands approximately 196, 152 and 93 kDa in size. The relative intensities of the bands in these extracts were merozoites > sporozoites >>> oocysts, suggesting the biosynthesis of these proteins is developmentally related. Feed supplementation with 60 ppm quizalofop, a known inhibitor of ACC, significantly reversed weight gain depression in chickens severely infected with E. maxima, but not with E. acervulina or E. tenella, suggesting the presence of ACC in E. maxima, at least. Molecular and biochemical characterization of the biotin-containing proteins in avian Eimeria is continuing with the goal of understanding their roles in the growth and development of these economically important parasites.